74 lines
3.4 KiB
Markdown
74 lines
3.4 KiB
Markdown
[equal.range]
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# 26 Algorithms library [[algorithms]](./#algorithms)
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## 26.8 Sorting and related operations [[alg.sorting]](alg.sorting#equal.range)
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### 26.8.4 Binary search [[alg.binary.search]](alg.binary.search#equal.range)
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#### 26.8.4.4 equal_range [equal.range]
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[ð](#lib:equal_range)
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`template<class ForwardIterator, class T = iterator_traits<ForwardIterator>::value_type>
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constexpr pair<ForwardIterator, ForwardIterator>
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equal_range(ForwardIterator first,
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ForwardIterator last, const T& value);
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template<class ForwardIterator, class T = iterator_traits<ForwardIterator>::value_type,
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class Compare>
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constexpr pair<ForwardIterator, ForwardIterator>
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equal_range(ForwardIterator first,
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ForwardIterator last, const T& value,
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Compare comp);
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template<[forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_iterator [iterator.concept.forward]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I> S, class Proj = identity,
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class T = projected_value_t<I, Proj>,
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[indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<const T*, projected<I, Proj>> Comp = ranges::less>
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constexpr subrange<I>
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ranges::equal_range(I first, S last, const T& value, Comp comp = {}, Proj proj = {});
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template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
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class T = projected_value_t<iterator_t<R>, Proj>,
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[indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<const T*, projected<iterator_t<R>, Proj>> Comp =
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ranges::less>
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constexpr borrowed_subrange_t<R>
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ranges::equal_range(R&& r, const T& value, Comp comp = {}, Proj proj = {});
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9538)
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Let comp be less{} andproj be identity{} for overloads with no parameters by those names[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9543)
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*Preconditions*: The elements e of [first, last)
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are partitioned with respect to the expressionsbool(invoke(comp, invoke(proj, e), value)) and!bool(invoke(comp, value, invoke(proj, e)))[.](#2.sentence-1)
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Also, for all elements e of [first, last),bool(comp(e, value)) implies !bool(comp(value, e)) for the overloads in namespace std[.](#2.sentence-2)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9553)
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*Returns*:
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- [(3.1)](#3.1)
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For the overloads in namespace std:{lower_bound(first, last, value, comp),
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upper_bound(first, last, value, comp)}
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- [(3.2)](#3.2)
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For the overloads in namespace ranges:{ranges::lower_bound(first, last, value, comp, proj),
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ranges::upper_bound(first, last, value, comp, proj)}
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9570)
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*Complexity*: At most2âlog2(last - first)+O(1) comparisons and projections[.](#4.sentence-1)
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